Question: This striking Australian mystery bird is part of a taxon that has several avian ecological equivalents in other parts of the world. Can you identify this distinctive species and its taxonomic family, and tell me which other avian groups perform similar ecological functions?

Response: This is an adult male eastern spinebill, Acanthorhynchus tenuirostris. This bird is placed into the family, Meliphagidae (the honeyeaters), a rather large group of passerines with many members that feed on nectar of Australasian flowering plants. One morphological trait that many meliphagids have is a distinctive brush-tipped tongue, which varies by species in length and in the brush's morphology, but which is specially adapted to soak up liquids. These birds lap nectar from flowers much as cats lap milk from a dish, although the birds' lapping movements are much faster. When the liquid-moistened brush is pulled back into the bird's mouth, the brush is squeezed against the upper mandible to push all fluid out so the bird can swallow it.

As mystery bird commenter, icancho, pointed out so efficiently, the meliphagids are "[c]onvergent on members of several other groups, such as Drepanididae, Nectarinidae, Promeropidae, Melanocharitidae, Mohoidae and, in terms of bill shape & feeding ecology, Trochilidae."

There are only two spinebill species, and they differ from the other honeyeaters by supplementing their nectar diet with substantial quantities of insects for added protein when breeding. Interestingly, DNA work shows that the spinebills are a sister group to all other honeyeaters; diverging earlier than all other meliphagid species. This indicates that the honeyeaters became more specialised on nectar as they diverged.

Eastern spinebills are adaptable, feeding from the flowers of both native and exotic plants. Since they are one of the smallest of Australia's honeyeaters, they sometimes hover like a hummingbird when feeding, although they usually feed whilst perched. They are found in a variety of habitats along the eastern coast of Australia, including dry sclerophyll forest, scrub and heathland and even in well-planted urban gardens.

Here is a video that captures several male and female spinebills feeding from a variety of flowers in the videographer's garden (no hovering, alas; video uploaded 10 April 2010):